One thing I really believe the game could use is the ability to train Hearthlings on jobs.
My first idea was a sub-job, where you could assign a new villager to work as an apprentice to a current worker, but you already have “Apprentice” as a title for workers who are just getting started. It did give me a couple of other ideas that I think could be really useful.
Training should be available, maybe only at expert levels, but once you get a level 5 Mason, they should be able to work along-side a new Mason to get them leveled up quickly so that you can advance the new villager to Potter (and Farmer/Cook, Blacksmith/Engineer, etc.). There are already some parts that can be used to lay the foundation of this by having different levels of workshops; a Blacksmith will use the Forge until they advance, and then stick with just the Anvil, and their student would be the only one using the Forge, getting an XP boost for having a Master nearby (like the Knight aura).
Another idea would be giving Hearthlings the ability to work a previous job, but not be happy about doing it. I would think this would require a new checkbox in the worker screen (“Job” and “Prior Job”), but think of an Engineer having to go back to his Blacksmith roots to get those Iron Ingots made. He’s grumpy about having to resort to such menial tasks, but he can do it, so he does.
That’d be so useful! (Especially when towns can have 30+ hearthlings) And maybe to add on to that, when two masters are near each other they’ll produce more fine items because they are bouncing ideas off of each other, which of course leads to improvement.
Overall I love your idea though! 
Sounds like a great idea in my opinion!
I think this would also be very good for military units. So if you lose one footman or knight or archer, other (high level) footman, knights or archers can train new ones, so that they level up faster, so you can recover from a loss quite fast. 
Welcome to Dicourse @Atras
This is a really good idea, and I think sooo many others would agree. This would definetly speed up the mid to late game progress. Though I think the balance of the leveling up would be off. I mean, I think it would get a bit too easy then.(<— Personal opinion) But this could work out really well if it got balanced well.
Thx for reading 
This, so much… This will be so helpfull…